The guard plates presently used for protecting lock cylinders are generally disposed over the cylinder on the outside surface of the door. Such plates prevent intruders from penetrating the cylinder and thus opening the door.
One disadvantage of these guard plates is that the keyhole portion of the cylinder is still accessible to unwanted intruders. Thus, it is an object of this invention to provide a guard plate which will also cover the keyhole portion of the cylinder. In this way, the lock and its cylinder will be protected even more from tampering and from picking. Furthermore, the improved guard plate of this invention prevents glue or other foreign materials from getting into the keyhole or the cylinder itself.
Another feature of the invention is the inclusion of an alarm system. If an intruder attempts to open the guard plate in an incorrect manner, an alarm will sound, thus offering even more protection.